The present invention relates to a method of operation for a processing machine, especially for a machine tool.
The present invention further relates to a system program which includes machine code that is able to be executed by a numerical controller, wherein the effect of the processing of the machine code by the numerical controller is that the numerical controller executes such an operating method.
The present invention further relates to a numerical controller which is programmed with a system program of this type.
The present invention further relates to a processing machine, especially a machine tool.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
With processing machines—for example machine tools—the position-regulated axes are moved in a coordinated manner so that the workpiece is processed by means of the tool according to processing defined by the parts program.
Typically only the so-called TCP (=tool center point), i.e. a central point of the tool which acts on the workpiece during processing, is predetermined by means of the parts program. The real kinematics of the processing machine is not taken into account in predetermining the TCP. Because of the fact that the real kinematics of the processing machine is not known in advance within the context of establishing the parts program, no check can be made within the context of the parts program as to whether a desired processing defined by the parts program by means of the real processing machine is possible or not. In particular no check can be made as to whether, as part of the movement processes to be undertaken by the real kinematics of processing machine, the result will be undesired collisions of the tool with machine elements of the processing machine or the workpiece or undesired collisions of the machine elements with each other or with the workpiece.
To avoid such collisions virtual volumes (=protection bodies) are assigned to the tool, the workpiece and the machine elements by the numerical controller. The protection bodies can be defined—both in the prior art and also within the context of the present invention—as real volumes. As an alternative it is possible to define the protection bodies by their envelope curves. Therefore, when reference is made below to the protection bodies or the corresponding volumes, this can likewise be taken to mean the envelope curves as an alternative.
According to the real kinematics of the processing machine the protection bodies are linked. They are moved virtually by the numerical controller as part of a so-called preamble, i.e. before the real activation of the axes, in accordance with the movement to be realized. The numerical controller checks whether, within the context of this movement, the protection bodies intrude into or touch each other. If they do, the protection bodies do not remain disjoint from one another. Thus there is an unwanted collision. Otherwise the real execution of the parts program can take place.
In the parts program the setpoint position values are stored as ideal setpoint position values for an ideal processing machine. In the establishment of the parts program the assumption has therefore been made that the respective positioning of the tool relative to the workpiece corresponds entirely exactly to the predetermined setpoint values. Real processing machines exhibit deviations however. These deviations for example include offsets, zero point displacements, linear deviations and rotational deviations. Therefore a field is often stored in the numerical controller which specifies the resulting position error for the respective combination of setpoint axis values. A position error field is therefore known to the numerical controller, which specifies for any given setpoint axis values the actual position that the tool assumes relative to the workpiece when the position-regulated axes are positioned at the respective setpoint axis values. The respective position error is defined typically as a deviation from the corresponding ideal position which would be produced if the processing machine were to be constructed entirely error-free. As an alternative the actual position itself can be stored. Regardless of which method of operation is adopted, the numerical controller is capable, as a result of the position error field, of correcting the setpoint axis value accordingly, so that as a result of the TCP will be positioned correctly, i.e. in accordance with the specification by the parts program. The respective position error typically includes—both in the prior art and also within the context of the present invention—at least the (translational) positioning errors. It can additionally—both in the prior art and also within the context of the present, invention—include a (rotational) orientation error with one, two or three angles.
In the prior art the position error field is only used for correction of the real activation, but not as part of the preliminary phase for determining the positions of the protection bodies and for determining collisions resulting therefrom.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved method and system by which collisions can be reliably avoided.